Mandrel



June 3, 1930. H. R. WILSON ET AL MANDREL Filed Jan. 14. 1928 wat..

'A HOWARD R. WILSON, or cARNEeIE,

Patented June 3, y1.930

,Unirse s'rarlssv PATENT JoFFrCEA ;g

PENNSYLVANIA, AND WALLACE W. SNirJJH,v or yCHL- cAGo, ILLrNoIs'` y MANDBEL l Application led January 14, 1928. Serial No. 246,818.

Our invention relates to mandrels and has for its object the provision of means by which a lock nut on the spindle of the mandrel will prevent a wheel carrie-d by the mandrel from being released by strainuapplied to the wheel.

, While this device has other uses, it is designed particularly for supporting and holding the grinding and polishing wheels used by dentists.4

The accompanying drawings represent a dentists mandrel drawn to a scale four times `the actual size for the sake of clearness, and

in said drawings Fig. 1 is an elevation, partly in section, of a mandrel supporting a grinding Wheel;

Fig. 2 is a similar view with a paper disk supported in position; and

Fig. 3 is a section online'S-S of Fig. 1. The shank 10 is adapted to be secured to the vflexible shaft of a dental engine in the ordinary manner. The outer portion is en- `larged and screw threaded as shown at 11.

diameter of this shoulder is less than the di-v ameter of the countersink 17, and preferably of about the same diameter as head 12.

The pitch of the threads on screw 14 is i slightly less than the pitch of the threads on the enlargement 11, andy both have their pitches in the same direction. That is, both screws have right hand threads, or both may have left hand threads, but one cannot have right hand and the other lefthand.

In placing a wheel W on the mandrel, the nut is backed up until the head 12 projects beyond the face of it. The screw 14 is then applied to clamp and hold the wheel in the ordinary manner. With this accomlplished, the lock nut 15. is screwed up against therear face of the wheel.

, When the wheel is used in grinding,lif the resistance'is in the direction to tighten the screw 14, then any turning ,of the screw would result in 'clamping the wheel more4 tightly against the head 12 of the Vdriving shank 10. p n j If the resistance is in the direction 4to loosen the screw, then wehave the condition that the nut 15 is screwed against the rear face of the wheel after the screw 14 was screwed home. Under these conditions the main clamping action is betwen the shoulder 19 and the face ofthe nut 15. But the bearing face of the nut is of larger diameter than the face 0f the shoulderlQ against the wheel.A As Ia consequence there is a greater turning friction on the nut than onthe screw. But the thread of the nut is of coarser pitch than the thread' of the screw 14. The result is that if there is any turning action, it will be'that of the nut to increase the degree of clamping be-` tween nut and screw. y

Briefly, if the action is; tok tighten the screw 14, then the screw cannot become loose and let the wheel ily oi. If the turning action is one which ywould normally loosen the screw, then the superior diameter of the nut andits coarser thread act to clamp the wheel, nut. and screw together, and the wheel cannot ly oii. i v f We may look at vthis matter in another way.

The combination consists of four parts, they spindle, the screw, the nut and the part held in place, which in this case isthe wheel W. The part held, here enters into ,the combinationbecause it aii'ects the relationship of the screw andV nut with respecttojeach other.v

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'Ihe' clamped condition vcan be released by" i turning either the screw or the nut with, respect to the other three parts, but no release can be had by attemptingtogturn the wheel and spindle with respect to each other with-v out rst releasing either the screw or the nut.

In Fig. 2 we have shown a paper polishing wheel D held in place. Here, as before, the wheel is clamped in the ordinary manner between the screw and the head 12, and then the nut is screwed up aga-inst the rear face of thedisk D. In this operation the disk is given a crimp atthe point 20, but is held flat between the face 0f the nut and the annular surface'around the shoulder 19.k

What We claim is v n 5 1.Means for clamping together two parts u ingente-ey @sa nies-iat' O-'pjaoeitL-e that WALL-AGE :Wr SMITH" sa l 

